The present invention relates to a damping-force control mechanism in a hydraulic shock absorber for use with a suspension system of automotive vehicles.
In hydraulic shock absorbers for automotive vehicles, the damping-force can preferably be controlled in accordance with driver's taste, running conditions of vehicles, carrying conditions, and so on. The damping-force is required to be controlled particularly with such vehicles as a motorbicycle, since such vehicle is lightweight but involves a considerable variation in load i.e. a vehicle with goods, multiple use vehicles, etc.
An attempt has already been made to meet the needs as described above by providing an arrangement wherein a partitioning member such as a piston disposed within the shock absorber has ports made therein through which oil within the shock absorber flows upon operation of the shock absorber. A stepwise rotatable orifice plate placed over an end surface of the partitioning member to which the ports are open; the orifice plate has a plurality of orifices different in diameter made therein which are selectively placed in communication with the port upon rotation of the orifice plate, and the damping-force may be controlled with change in flow resistance of an orifice in communication with the port. However, the conventional damping-force control mechanism as noted above possesses a disadvantage in which an error in machining of the orifices can produce substantial irregurality in the amount of change in the damping-force generated every step of rotation of the orifice plate.